1. Field of the Invention
This invention relates to an improved superconductive Josephson junction logic circuit, and more particularly, to a novel Josephson junction AND gate logic circuit.
2. Related Applications
This invention is an improvement of our co-pending "Three Josephson Junction Direct Coupled Isolation Circuit", Ser. No. 298,148 filed Aug. 31, 1981 which shows and describes a novel Josephson junction logic circuit preferably employed as an OR logic circuit but could be employed as an AND logic circuit.
3. Description of the Prior Art
The prior art logic circuits employing Josephson junction devices are generally classified in U.S. Class 307, subclass 306 with superconductive devices. The prior art includes IBM Journal of Research and Development, Vol. 24, Number 2, March 1980 at pages 130-132. This IBM article discloses at page 132 a two input AND gate Josephson junction circuit employing three interferometers having eight Josephson junctions. This AND gate circuit is inductively coupled at the inputs and at the outputs which places limitations on the speed of operation of this complex circuit.
Another form of Josephson junction circuit which may be adapted to AND gate logic is disclosed in IEEE, International Electron Devices meeting at Washington, D.C., Dec. 3-5, 1979 at pages 482-484. This Josephson junction circuit is based on direct coupled logic (DCL) wherein the two inputs to the AND gate are directly coupled to the logic circuitry. This Josephson junction circuit includes ten Josephson junctions arranged as two OR logic functions followed by amplification followed by an output stage which includes an interferometer.
Both of the above Josephson junction circuits are complex which makes them undesirable for integrated circuit implementation.
It would be desirable to provide a new Josephson junction AND gate logic circuit which can be employed as a logic module building block and which has two direct coupled inputs and multiple outputs having a large margin of safety for driving identical logic module loads.